Differential

ABSTRACT

A differential has a housing with two coaxial sun gears and two pairs of planetary pinions carried by the housing. The planetary pinions of each pair mesh with each other as well as with their respective sun gears so that two pinions, namely one in each pair, are capable of rotation in an orbit about its associated sun gear. The planetary pinion pairs transmit driving torque to the sun gears upon rotation of the housing yet permit differential rotation of the sun gears. Furthermore, the sun gears integrally include hollow tubular hubs that project outwardly from opposite sides of the housing so that the shaft or axles to be driven can be quickly connected to the hubs without the necessity of disassembly of the differential unit. Spur gears are used throughout, which simplifies and reduces the cost of the differential unit.

United States Patent 1191 Wharton 1 51 Oct. 30, 1973 DIFFERENTIAL IPrimary Examiner-Charles J. Myhre [75] Inventor: Richard F. Wharton,Chicago, Ill. 4 Exammer Th0mas Perry Attorney-Robert W. Beart et al.[73] Assignee: Illinois Tool Works lnc., Chicago,.

Ill. [22] Filed: June 29, 1971' [57] ABSTRACT A differential has ahousing with two coaxial sun ears [21] Appl' 157953 and two pairs ofplanetary pinions carried by the sousing. The planetary pinions of each.pair mesh with each [52] US. Cl. 74/714 other as well as with theirrespective sun gears so that [51] F161 1/42 two pinions, namely one ineach pair, are capable of [58] Field of Search 74/714, 710,713 rotationin an orbit about its associated sun gear. The planetary pinion pairstransmit diriving torque to the [56] References Cited sun gears uponrotation of the'housing yet permit dif- UNHED STATES PATENTS ferentialrotation of the sun gears. Furthermore, the 691,591 1/1902 Brown 74/714sun.gears mtegrany mclude P Y tubular hubs h 732327 6/1903 warner 1 74pro ect outwardly from oppos1te s des of the housmg 827095 7,1906 Gray n74/7l4 so that the shaft or axles to be driven can be quickly 900,85710/1908 J ff 74/714 connected to the hubs without the necessity ofdisas- 1,030,379 6/1912 Benson..... 74/714 X sembly of the differentialunit. Spur gears are used 1,987,674 1/1935 Ford 74/714 throughout, whichsimplifies and reduces the cost of 2,788,679 4/1957 Mott 74/714 thdifferential nit 3,365,984 Musgrave 74/713 1 Claim, 6 Drawing FiguresPAIENTEUnmo mu SHEET 10F 2 01 mad/z;

DIFFERENTIAL BACKGROUND OF THE INVENTION This invention relates to adifferential of a type that is particularly suitable for garden tractorsand similar small vehicles.

In the manufacture of small garden tractors and like vehicles, it iscommon for the manufacturer top'urchase differential units forincorporation into his vehicle. In such situations, the design of thedifferential has been such that the differential unit must be originallymanufactured with integral axles because the sun gears must be coupledby keying or otherwise to the axles that are to be driven by the unit.This has seriously limited the vehicle manufacturer in being able towork on the axles separately of the differential unit. Obviously, such asituation is costly and prevents the vehicle manufacturer fromeconomically substituting other axles.

OBJECTS AND SUMMARY OF THE INVENTION An object of the present inventionis to provide a differential which is so constructed and arranged thatthe axles or shafts to be driven may be coupled to the differential unitwithout the necessity of even partial disassembly thereof, therebysimplifying the incorporation of the unit into a tractor or the like.

A further object of the present invention is to provide a differentialof the type stated in which a driving gear or sprocket may be readilyattached to the differential housing so that the latter may be rotatedfor applying, through the gearing within the housing, driving torque tothe axles to be driven by the differential unit.

Another object of the present invention is to provide a differential ofthe type stated which is relatively inexpensive to manufacture bothinterms of the cost of component parts and in terms of ease of assembly.Spur gears are used throughout in contrast to the customary bevelledgears usually found in differentials.

In accordance with the foregoing objects, the invention contemplates adifferential unit having coaxial sun gears which may be differentiallyrotated through planetary gearing carried by the differential housing,whereby the'rotating housing transmits, through the planetary gearing,driving torque to the sun gears. The sun gears are characterized asintegrally including tubular hubs that project outwardly from oppositesides of the differential housing. As a result, the axles or othershafts to be driven by the differential may be easily inserted into thebores of the hubs. Consequently, the user (e.g., the tractormanufacturer) may use his own axles for the particular size of tractorin which the differential unit is to be incorporated. The hubs arepreferably pre-drilled for receiving roll pins to lock the axlestherein, it being necessary simply to drill each axle with a diametralhole for receiving the 01] pin. Splining of the hub bore or of thedriven axle or shaft is not necessary. Of course, the axle end. must beof a proper size to fit into the hub bore. I

The housing need not, and preferably is not, equipped with a drivesprocket, thereby enabling the user to use a drive sprocket or likedriving member of his own choosing. For this purpose, however, thehousing has peripheral flanges with bolt holes whereby a sprocket with agenerally rectangular central opening may be readily bolted to thehousing roughly at the dicular to the plane of the driving sprocket, sothat the mid-plane thereof. A feature of the invention is that thecentral opening of the sprocket can serve to substantially hold thehousing halves together and thereby reduce the number of fastenersneeded to lock the housing halves together.

BRIEF DESCRIPTION OF THE FIGURES In the drawing:

FIG. 1 is a sectional view taken along line 1-1 of FIG. 2 and showing adifferential unit constructed in accordance with and embodying thepresent invention;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1;

' FIG. 3 is a fragmentary perspective view, somewhat diagrammatic inform, and showing the gearing within the differential unit;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 1;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4; and

FIG; 6 is a fragmentary sectional view taken along line 66 of FIG. 4,but showing the housing and parts therein in elevation.

DETAILED DESCRIPTION Referring now in more detail to the drawing, whichillustrates a preferred embodiment of the present invention, 2designates a differential comprising a housing 4 that is formed of apair of similar hollow die cast members 6, 8 having peripheral bosses10. The corresponding bosses 10 of the respective housing members 6, 8are in abutting relationship and receive bolt and nut assemblies 12 bywhich the housing members 6,8 are secured together. Formed inthe'housing members 6,8 centrally of each are-bores 14, 16 which, whenthe housing members are assembled, are coaxial. The bores 14, 16communicate with the interior or chamber 18 of the housing 4.

Rotatably mounted within the housing chamber 18 centrally thereof arecoaxial sun gears 20, 22 which integrally include tubular hub portions24, 26 that are journalled in the bores 14, 16 and are of such lengthsthat they project outwardly beyond opposite sides of the housing. Formedin the housing members 6, 8 and. surrounding the respective hub portions24, 26 are annular grooves 28 for receiving a substantial charge oflubricant. Each housing member 6, 8 also integrally includes generallysemicircular central sections 30, 32 which together constitute a spacerto maintain the sun gears 20, 22 a small distance axially apart. Withinthe sections 30 and 32, an annular liner 3] is provided. The liner 31functions as a bearing about the inner ends of the sun gears 20 and 22.

The peripheral portions of the chamber 18 are of similar, generallyoval-shaped configuration and are each sized for receiving planetarygearing. In the form of the invention herein shown, the planetarygearing includes two pairs of meshing pinions, namely a first pair 34,36 and a second pair 38, 40. The pinions 34, 36 mesh over a portion oftheir respective tooth widths and the same is true of the pinions 38,40. The pinions 36, 40 are apart and each mesh with the sun gear 22 andare capable of movement in an orbit there about. Similarly, the pinions34, 36 are 180 apart and each mesh with the sun gear 20 and are capableof movement in an orbit thereabout. Consequently, when torque is appliedto the housing 4 the meshing pinion pair 34, 36 and the like meshingpinion pair 38, 40 apply driving torque to rotate the respective sungears 20, 22. If one of the sun gears, for example sun gear 22, isexternally strained against rotation, the other sun gear will still bedriven by the rotating housing. However, the planetary gearing formed bythe pinions 36, 40, namely the pinions that mesh with the restrainedgear, will simply orbit about the restrained gear. Thus, the gearingarrangement provides differential driving for the two sun gears 20, 22.

The pinions 34, 36 are rotatable on parallel pinion shafts 42, 44, andsimilarly the pinions 38, 40 are rotatable on parallel pinion shafts 46,48. Formed in the respective housing members 6, 8 are grooves 50 thatopen toward the opposite housing member. There is a groove for receivingan end of each of the shafts 42, 44, 46, 48. As seen in FIG. 1, suchshaft end is the shorter end as is noted with respect to the shafts 44,48, and the pinion shafts are furthermore retained against significantaxial movement by abutment against interior surfaces of the housingmembers. As seen in FIG. 2, the housing members 6, 8 meet along aparting region that includes not only the plane passing through the axisof rotation of the sun gears 20, 22, but also at tongues or projections52. These projections 52 extend from one of the housing members intorecesses 54 in the other housing member so as to engage and retain theshorter end of each pinion shaft in place in its associated groove 50when the housing members are bolted together. Since the adjacentplanetary pinions are in mesh over a substantial portion of their toothwidth and the pinions mesh with the sun gears, as aforesaid, thearrangement keeps the pinion shafts parallel. Generally speaking thepinion shafts are held reasonably rigid; however, to the extent that theshafts rotatably creep or to the extent that the friction between eachpinion shaft departs from an antifriction bearing, the differential willhave a limited slip characteristic.

lntegrally formed on the peripheries of the housing members 6, 8opposite to the parting region of the members when the two areassembled, are flanges 56, 58 for receiving bolt and nut assemblies 60.The bolts of the bolt and nut assemblies 60 are adapted to pass througha sprocket 62 which has a central opening 64 that is sized and shapedfor receiving the housing 4. Accordingly, the sprocket 62 has a centralopening that is somewhat rectangularly shaped but with rounded corners.A drive chain 66 is trained around the drive sprocket 62 to rotate thehousing 4, the drive chain 66 receiving its power from the engine of thetractor or other vehicle with which the differential unit is used.

The differential unit 2 is adapted to drive coaxial shafts such asvehicle axles 68, 70 which are adapted to telescope within the bores 72,74 of the hub portions 24, 26. Outside of the housing 4 the hub portions24, 26 have holes 76 for receiving roll pins 78, the roll pins passingthrough diametral holes in the axles 68, 70, whereby the axles 68, 70are rigidly secured respectively to the hub portions 24, 26. Thedifferential unit 2 is manufactured with the holes 76 already formed sothat in order to couple the axles 68, 70 to the respective hub portions24, 26 it is merely necessary to drill the diametral holes in the axles68, 70. then insert the axles within the hub portions, and then mountthe roll pins 78 in place. A complete or even a partial disassembly ofthe differential unit is not necessary, thus rendering the unit readilyconnectable to the axles 68,70.

The invention is claimed as follows:

1. A differential comprising a housing, a first sun gear in said housingand being rotatable relative thereto, a second sun gear in said housingand being rotatable relative thereto, said sun gears being coaxial, saidhousing comprising two hollow members securedtogether and meeting alonga parting region, said region including therein a plane in which theaxis of rotation of said sun gears is located, first planetary gearmeans within said housing and mounted on a first shaft, said firstplanetary gear means meshing with said first sun gear and movable in anorbit thereabout, second planetary gear means within housing and mountedon a second shaft, said hollow members having grooves for receiving saidshafts and projections for engaging one end of each shaft in itsassociated groove, said second planetary gear means meshing with saidsecond sun gear and movable in an orbit thereabout, said planetary gearsmeshing and each being carried by the housing upon rotation thereof toapply driving torque to said sun gears and permit differential rotationof said sun gears with the projections and mesh of said pinionscooperating to maintain said shafts in substantially parallelrelationship within said housing, each of said sun gears having a hubportion projecting outwardly from the housing for coupling to coaxialshafts to be driven by rotation of the housing, and a sprocket having acentral opening, said hollow members projecting through said centralopening and extending substantial distances on opposite sides of thesprocket and with the peripheral part of the housing engaging thesprocket at said central opening whereby the sprocket serves to hold themembers assembled, said parting region plane being perpendicular to theplane of the sprocket, and means for securing said sprocket to saidhousing.

1. A differential comprising a housing, a first sun gear in said housingand being rotatable relative thereto, a second sun gear in said housingand being rotatable relative thereto, said sun gears being coaxial, saidhousing comprising two hollow members secured together and meeting alonga parTing region, said region including therein a plane in which theaxis of rotation of said sun gears is located, first planetary gearmeans within said housing and mounted on a first shaft, said firstplanetary gear means meshing with said first sun gear and movable in anorbit thereabout, second planetary gear means within said housing andmounted on a second shaft, said hollow members having grooves forreceiving said shafts and projections for engaging one end of each shaftin its associated groove, said second planetary gear means meshing withsaid second sun gear and movable in an orbit thereabout, said planetarygears meshing and each being carried by the housing upon rotationthereof to apply driving torque to said sun gears and permitdifferential rotation of said sun gears with the projections and mesh ofsaid pinions cooperating to maintain said shafts in substantiallyparallel relationship within said housing, each of said sun gears havinga hub portion projecting outwardly from the housing for coupling tocoaxial shafts to be driven by rotation of the housing, and a sprockethaving a central opening, said hollow members projecting through saidcentral opening and extending substantial distances on opposite sides ofthe sprocket and with the peripheral part of the housing engaging thesprocket at said central opening whereby the sprocket serves to hold themembers assembled, said parting region plane being perpendicular to theplane of the sprocket, and means for securing said sprocket to saidhousing.